Disposable wearable article

ABSTRACT

A disposable wearable article includes an elastic film stretchable structure in which an elastic film is laminated between a first sheet layer and a second sheet layer. The first sheet layer and the second sheet layer are bonded to each other through holes passing through the elastic film with many bonded portions arranged at intervals. A region having the elastic film stretchable structure includes a stretchable region that elastically stretches and contracts together with the elastic film. The stretchable region includes a plurality of elastic films disposed so as to have an overlapping portion. The number of laminated layers of the elastic film in a region located in an intermediate portion of the stretchable region in an orthogonal direction (XD) orthogonal to a stretchable direction (ED) is different from that in each of second regions adjacent to both sides of the first region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. national stage application of InternationalApplication PCT/JP2018/017398, filed May 1, 2018, which internationalapplication was published on Jan. 24, 2019, as International PublicationWO 2019/017037 in the Japanese language. The International Applicationclaims priority of Japanese Patent Application No. 2017-140223, filedJul. 19, 2017. The international application and Japanese applicationare both incorporated herein by reference, in entirety.

TECHNICAL FIELD

The present invention relates to a disposable wearable article having anelastic film stretchable structure in which an elastic film issandwiched between sheet layers.

BACKGROUND ART

In a disposable wearable article such as a disposable diaper or asanitary napkin, in order to improve fitting to a body surface,elasticity is generally imparted to an appropriate place such asportions around legs or a lower torso. As a technique for impartingelasticity, conventionally, a technique for disposing and fixing manyelongated elastically stretchable members such as rubber threads in astate in which the elongated elastically stretchable members arestretched in a longitudinal direction has been widely adopted. However,as a technique having excellent surface fitting, a technique forattaching an elastic film in a state where the elastic film is stretchedin an elasticity imparting direction has also been proposed. (Forexample, see Patent Literatures 1 to 3).

A stretchable structure in which this elastic film is sandwiched betweensheet layers (hereinafter also referred to as an elastic filmstretchable structure) is obtained by laminating an elastic film betweena first sheet layer in which a stretchable region is formed of anonwoven fabric or the like and a second sheet layer formed of anonwoven fabric or the like, and bonding the first sheet layer and thesecond sheet layer to each other through through-holes formed in theelastic film or via the elastic film with many bonded portions arrangedat intervals in a stretchable direction and a direction orthogonalthereto in a state where the elastic film is stretched in thestretchable direction. In the stretchable region having such an elasticfilm stretchable structure, in a natural length state, as the elasticfilm contracts between the bonded portions, an interval between thebonded portions becomes narrower, and contraction wrinkles extending ina direction crossing the stretchable direction are formed between thebonded portions in the first sheet layer and the second sheet layer. Onthe contrary, at the time of stretch, as the elastic film stretchesbetween the bonded portions, an interval between the bonded portions andcontraction wrinkles in the first sheet layer and the second sheet layerbecome wider, and elastic stretch is possible until the first sheetlayer and the second sheet layer are fully unfolded. This elastic filmstretchable structure has an advantage that the through-holes of theelastic film contribute to improvement of air permeability as well asexcellent surface fitting.

A disposable wearable article is required to have different fittingsdepending on a site. Therefore, an intermediate portion of a stretchableregion in a direction orthogonal to a stretchable direction desirablyhas a contraction force at the time of stretch (hereinafter simplyreferred to as contraction force) different from a contraction force inboth sides of the intermediate portion. In this regard, the elastic filmstretchable structure can also change a contraction force at the time ofstretch in a direction orthogonal to a stretchable direction dependingon the area ratio or pattern of bonded portions.

However, only by selecting the area ratio and pattern of the bondedportions, only the contraction force can be reduced, and a contractionratio also changes. Therefore, this affects an appearance in a naturallength state.

Meanwhile, as described in Patent Literatures 2 and 3, a contractionforce can be changed depending on a site, for example, a stretchableregion due to an elastic film is disposed separately from a stretchableregion due to a rubber thread to make a contraction force at a waistportion stronger than that on a crotch side. However, a contractionforce does not change within a stretchable region of an elastic filmstretchable structure.

The present applicant has proposed an elastic film stretchable structurehaving a stretchable region in which a stretch rate changes continuously(see Patent Literature 4), and an elastic film stretchable structure inwhich an elastic film, a first sheet layer, and a second sheet layer arefolded back at an edge of an opening, and the edge portion of theopening is tightened more firmly (see Patent Literature 5).

However, in the elastic film stretchable structure described in PatentLiterature 4, a contraction force changes continuously, and cannot bechanged discontinuously. Even if a contraction force is changed in adirection orthogonal to a stretchable direction, it is difficult toincrease a width of the change.

The elastic film stretchable structure described in Patent Literature 5is based on an assumption that the elastic film, the first sheet layer,and the second sheet layer are folded back. Therefore, an intermediateportion of a stretchable region in a direction orthogonal to astretchable direction cannot be tightened more firmly than both sides ofthe intermediate portion.

CITATION LIST Patent Literature

Patent Literature 1: JP 2004-532758 A

Patent Literature 2: JP 4987967 B2

Patent Literature 3: JP 5292586 B2

Patent Literature 4: JP 2016-189824 A

Patent Literature 5: JP 2016-190031 A

SUMMARY OF INVENTION Technical Problem

A main object of the present invention is to provide an elastic filmstretchable structure in which an intermediate region of a stretchableregion in a direction orthogonal to a stretchable direction has adifferent contraction force from each of adjacent regions adjacent toboth sides of the intermediate region.

Solution to Problem

Various aspects that have solved the above problem are as follows.

<First Aspect>

A disposable wearable article having an elastic film stretchablestructure in which an elastic film is laminated between a first sheetlayer and a second sheet layer, and the first sheet layer and the secondsheet layer are bonded to each other through holes passing through theelastic film or via the elastic film with many bonded portions arrangedat intervals,

a region having the elastic film stretchable structure including astretchable region that elastically stretches and contracts togetherwith the elastic film, in which

the stretchable region includes a plurality of elastic films disposed soas to have an overlapping portion, and

the number of laminated layers of the elastic film in a first regionlocated in an intermediate portion of the stretchable region in anorthogonal direction orthogonal to a stretchable direction is differentfrom that in each of second regions adjacent to both sides of the firstregion.

(Action and Effect)

In the present aspect, the number of laminated layers of the elasticfilm in the first region located in an intermediate portion of thestretchable region in an orthogonal direction orthogonal to astretchable direction is different from that in each of the secondregions adjacent to both sides of the first region. Therefore,regardless of a change in the pattern of the bonded portions or thestretch rate of the elastic film, a contraction force at the time ofstretch can be made different. That is, if the pattern of the bondedportions and the stretch rate of the elastic film are the same betweenthe first region and the second region, a contraction force in a regionwith a large number of laminated layers is relatively stronger, and acontraction force in a region with a small number of laminated layers isrelatively weaker. In addition, unlike a conventional form in which thenumber of laminated layers is increased by folding, there is nolimitation on the number or arrangement of portions with a large numberof laminated layers.

<Second Aspect>

The disposable wearable article according to the first aspect,including: a first elastic film extending from one of the second regionsto the first region; and a second elastic film extending from the othersecond region to the first region as the elastic film, in which

the one of the second regions includes only the first elastic film asthe elastic film,

the other second region includes only the second elastic film as theelastic film, and

the first region includes the first elastic film and the second elasticfilm as the elastic film.

(Action and Effect)

The number of elastic films, the number of laminated layers thereof, andarrangement thereof are not particularly limited. However, if the numberof laminated layers of the elastic film is large, manufacture may bedifficult, for example, it may be difficult to form bonded portions.Therefore, a simple structure as in the present aspect is preferable.

<Third Aspect>

The disposable wearable article according to the second aspect, in which

a stretch stress at the time of 4-times stretch in the stretchabledirection in the first elastic film is different from a stretch stressat the time of 4-times stretch in the stretchable direction in thesecond elastic film.

(Action and Effect)

As in the present aspect, by using the first elastic film and the secondelastic film having different stretch stresses, a contraction force canbe made different among the three regions consisting of the one of thesecond regions, the first region, and the other second region while thesimple structure of the second aspect is maintained.

<Fourth Aspect>

The disposable wearable article according to the second or third aspect,in which

an elongation at elastic limit of the one of the second regions isdifferent from that of the other second region, and the largerelongation at elastic limit thereof is the same as the elongation atelastic limit of the first region.

(Action and Effect)

When the first sheet layer and the second sheet layer are bonded to eachother in manufacture, if the stretch rates of the elastic films are madedifferent from each other, as in the present aspect, the elongation atelastic limit of one of the second regions is different from that of theother second region, and the larger elongation at elastic limit is thesame as the elongation at elastic limit of the first region. In thepresent aspect, when the stretchable region is stretched in thestretchable direction from an initial stage at which both the elasticfilms are in a natural length state, the stretchable region comes to awearing stage at which both the elastic films are in a stretched statethrough an intermediate stage at which one of the elastic films is in anatural length state, and the other elastic film is in a stretchedstate. Therefore, when the stretchable region is stretched for wearing,the first region initially stretches with the same stretch stress as thesecond region with a larger elongation at elastic limit, and the stretchstress is the strongest at a wearing stage. Therefore, the article iseasily worn, and obtains firm fitting in a wearing state.

<Fifth Aspect>

The disposable wearable article according to any one of the first tofourth aspects, which is an underpants-type disposable wearable articleincluding:

a front-back separated or front-back integrated outer member including afront body lower torso portion, a back body lower torso portion, and anintermediate portion located therebetween; and

an inner member attached to the outer member and extending from thefront body to the back body via a crotch portion, in which

both sides of the outer member in the front body are bonded to bothsides of the outer member in the back body to form a side seal portionand to form a waist opening and a pair of left and right leg openings,and

at least one of the outer member of the front body and the outer memberof the back body has the stretchable region that stretches and contractsin a width direction.

(Action and Effect)

In an underpants-type disposable wearable article, a stretchable regionthat stretches and contracts in a width direction is generally disposedin an outer member. In consideration of fitting to a bulge of a lowerabdomen portion and fitting to a bulge of a gluteal region, in at leastone of the outer member of the front body and the outer member of theback body, the first region of the stretchable region in a directionorthogonal to the stretchable direction preferably has a contractionforce different from each of the second regions adjacent to both sidesof the first region.

<Sixth Aspect>

The disposable wearable article according to any one of the first tofifth aspects, in which

the outer member of the front body has the stretchable region in thelower torso portion, and the outer member of the back body has thestretchable region from the lower torso portion to the intermediateportion,

each of the stretchable regions includes a first elastic film extendingfrom one of the second regions to the first region, and a second elasticfilm extending from the other second region to the first region as theelastic film,

the one of the second regions includes only the first elastic film asthe elastic film,

the other second region includes only the second elastic film as theelastic film,

the first region includes the first elastic film and the second elasticfilm as the elastic film,

the outer member of the front body has the first region in the lowertorso portion, and

the outer member of the back body has the first region in theintermediate portion.

(Action and Effect)

By disposing the first region in which the first elastic film and thesecond elastic film overlap with each other and the second regionincluding only the first elastic film or only the second elastic filmasymmetrically in a front-back direction as in the present aspect,favorable fitting to a lower abdomen portion and a lower gluteal region(gluteal groove) where a gap is easily generated is achieved. Inaddition, the position of the first region of the front body isdifferent from the position of the first region of the back body in theside seal portion. Therefore, the number of laminated layers of amaterial in the side seal portion does not become locally too large.This prevents deterioration of wearing feeling and sealing failure ofthe side seal portion.

<Seventh Aspect>

The disposable wearable article according to the sixth aspect, in which

in the first elastic film and the second elastic film, a stretch stressat the time of 4-times stretch in the stretchable direction in theelastic film on the waist opening side is weaker than that in theelastic film on the opposite side.

(Action and Effect)

As in the present aspect, by using the first elastic film and the secondelastic film having different stretch stresses, a portion where a gap iseasily generated at the time of wearing can be firmly tightened, and acontraction force of a portion closer to a waist opening than theportion where a gap is easily generated can be minimized to reducetightening feeling on the waist opening side.

Advantageous Effects of Invention

As described above, the present invention provides, for example, anelastic film stretchable structure in which an intermediate region of astretchable region in a direction orthogonal to a stretchable directionhas a different contraction force from each of adjacent regions adjacentto both sides of the intermediate region advantageously.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view (internal surface side) of an underpants-typedisposable diaper in an unfolded state.

FIG. 2 is a plan view (external surface side) of an underpants-typedisposable diaper in an unfolded state.

FIG. 3 is a plan view illustrating only a main part of anunderpants-type disposable diaper in an unfolded state.

FIG. 4(a) is a cross-sectional view taken along line C-C in FIG. 1 , andFIG. 4(b) is a cross-sectional view taken along line E-E in FIG. 1 .

FIG. 5 is a cross-sectional view taken along line A-A in FIG. 1 .

FIG. 6 is a cross-sectional view taken along line B-B in FIG. 1 .

FIG. 7(a) is a plan view of a main part of a stretchable region, FIG.7(b) is a cross-sectional view taken along line D-D in FIG. 7(a), FIG.7(c) is a cross-sectional view in a wearing state, and FIG. 7(d) is across-sectional view in a natural length state.

FIG. 8(a) is a trace view of a micrograph of a stretchable region of asample, taken from a plane direction, FIG. 8(b) is a trace view of ahigh magnification micrograph of a stretchable region of a sample, takenfrom a plane direction, and FIG. 8(c) is a trace view of a highmagnification micrograph of a stretchable region of a sample, taken froma perspective direction.

FIG. 9(a) is a plan view of a main part of a stretchable region, FIG.9(b) is a cross-sectional view taken along line D-D in FIG. 9(a), andFIG. 9(c) is a cross-sectional view in a wearing state, and FIG. 9(d) isa cross-sectional view in a natural length state.

FIG. 10(a) is a trace view of a micrograph of a stretchable region of asample, taken from a plane direction, FIG. 10(b) is a trace view of ahigh magnification micrograph of a stretchable region of a sample, takenfrom a plane direction, and FIG. 10(c) is a trace view of a highmagnification micrograph of a stretchable region of a sample, taken froma perspective direction.

FIG. 11(a) is a plan view of a main part of a non-stretchable region,FIG. 11(b) is a cross-sectional view taken along line D-D in FIG. 11(a),FIG. 11(c) is a cross-sectional view in a wearing state, and FIG. 11(d)is a cross-sectional view in a natural length state.

FIG. 12 is a trace view of a photograph of a non-stretchable region of asample.

FIG. 13 is an enlarged plan view of a main part of a non-stretchableregion.

FIG. 14 is a left side view schematically illustrating a wearing state.

FIG. 15 is a plan view (external surface side) of an underpants-typedisposable diaper in an unfolded state.

FIG. 16(a) is a cross-sectional view taken along line C-C in FIG. 15 ,and FIG. 16(b) is a cross-sectional view taken along line E-E in FIG. 15.

FIG. 17 is a cross-sectional view schematically illustrating across-section of a main part of an outer member that has stretched tosome extent.

FIG. 18 is a cross-sectional view schematically illustrating across-section of a main part of an outer member that has stretched tosome extent.

FIG. 19(a) is a trace view of a plane photograph of a bonded portionformed in a first welding form, and FIG. 19(b) is a trace view of aplane photograph of a bonded portion formed in a third welding form.

FIG. 20 is a plan view illustrating various arrangement examples ofbonded portions.

FIG. 21 is a schematic view of an ultrasonic sealing device.

FIG. 22 is a schematic perspective view of an ultrasonic sealing device.

FIG. 23(a) is a cross-sectional view taken along line C-C in FIG. 1 ,and FIG. 23(b) is a cross-sectional view taken along line E-E in FIG. 1.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the present invention will be described in detail withreference to the attached drawings. Note that a dotted pattern portionin a cross-sectional view illustrates a bonding means such as a hot meltadhesive.

FIGS. 1 to 6 illustrate an example of an underpants-type disposablediaper. This underpants-type disposable diaper (hereinafter also simplyreferred to as a diaper) includes an outer member 20 forming a frontbody F and a back body B, and an inner member 10 fixed to and integratedwith an inner surface of the outer member 20. The inner member 10 isformed by interposing an absorber 13 between a liquid pervious top sheet11 and a liquid impervious sheet 12. In manufacture, a back surface ofthe inner member 10 is bonded to an inner surface (upper surface) of theouter member 20 by a bonding means such as a hot melt adhesive.Thereafter, the inner member 10 and the outer member 20 are folded atthe center in a front-back direction LD (longitudinal direction) that isa boundary between the front body F and the back body B. Both sideportions thereof are bonded to each other by heat welding, a hot meltadhesive, or the like to form a side seal portion 21, thus forming anunderpants-type disposable diaper with a waist opening and a pair ofleft and right leg openings.

(Structure Example of Inner Member)

As illustrated in FIGS. 4 to 6 , the inner member 10 has a structure inwhich the absorber 13 is interposed between the top sheet 11 and theliquid impervious sheet 12 made of polyethylene or the like, and absorbsand holds an excretory liquid that has passed through the top sheet 11.The planar shape of the inner member 10 is not particularly limited, butis generally rectangular as illustrated in FIG. 1 .

As the top sheet 11 covering a front surface side (skin side) of theabsorber 13, a porous or non-porous nonwoven fabric or a porous plasticsheet is preferably used. Examples of a material fiber constituting thenonwoven fabric include a synthetic fiber such as a polyolefin-basedfiber including polyethylene and polypropylene, a polyester-based fiber,or a polyamide-based fiber, a regenerated fiber such as rayon or cupra,and a natural fiber such as cotton. A nonwoven fabric obtained by anappropriate processing method such as a spunlace method, a spunbondmethod, a thermal bond method, a melt blown method, or a needle punchmethod can be used. Among these processing methods, the spunlace methodis excellent from viewpoints of high flexibility and drapeability, andthe thermal bond method is excellent from viewpoints of bulkiness andsoftness. When many through-holes are formed in the top sheet 11, urineor the like is quickly absorbed, and an excellent dry touch property isachieved. The top sheet 11 is wound around a side edge portion of theabsorber 13 and extends to a back surface side of the absorber 13.

As the liquid impervious sheet 12 covering a back surface side (non-skinside) of the absorber 13, a liquid impervious plastic sheet such aspolyethylene or polypropylene is used. However, in recent years, amoisture permeable sheet is preferably used from a viewpoint ofpreventing stuffiness. The water shielding and moisture permeable sheetis a microporous sheet obtained by melt kneading an inorganic filler inan olefin resin such as polyethylene or polypropylene to form a sheet,and then stretching the sheet in a monoaxial or biaxial direction. Inthe illustrated example, the liquid impervious sheet 12 is folded backto a back surface side on both sides of the absorber 13 in the widthdirection together with the top sheet 11, but the liquid impervioussheet 12 is not limited thereto.

As the absorber 13, a known absorber, for example, an absorber obtainedby mixing or fixing a super absorbent polymer as necessary on the basisof a pulp fiber stack, an assembly of filaments such as celluloseacetate, or a nonwoven fabric can be used. The absorber 13 can bewrapped by a wrapping sheet 14 having liquid perviousness and a liquidholding property, such as crepe paper, as necessary, for holding theshape and a polymer, for example.

The shape of the absorber 13 is formed into a substantially hourglassshape having a narrowing portion 13N narrower than both the front andback sides at a crotch portion. The size of the narrowing portion 13Ncan be determined appropriately, but the length of the narrowing portion13N in the front-back direction can be about 20 to 50% of the maximumlength of a diaper. The width of the narrowest portion can be about 40to 60% of the maximum width of the absorber 13. In a case where such anarrowing portion 13N is included, if the planar shape of the innermember 10 is substantially rectangular, in a portion corresponding tothe narrowing portion 13N of the absorber 13 in the inner member 10, anon-absorber side portion 17 including no absorber 13 is formed.

Three-dimensional gathers 90 that fit a body surface are formed on bothsides of the inner member 10. As illustrated in FIGS. 5 and 6 , each ofthe three-dimensional gathers 90 includes a fixed portion 91 fixed to aside portion of a back surface of the inner member 10, a main unitportion 92 extending from the fixed portion 91 up to a side portion of asurface of the inner member 10 through a side of the inner member 10, afallen portion 93 formed by fixing front and back end portions of themain unit portion 92 to a side portion of a surface of the inner member10 (the top sheet 11 in the illustrated embodiment) in a fallen state,and a free portion 94 formed by making a portion between the fallenportions 93 non-fixed. Each of these portions is formed of a gathersheet 95 that is a duplicate sheet obtained by folding back a sheet suchas a nonwoven fabric. The gather sheet 95 is attached over the entirefront-back direction of the inner member 10. The fallen portion 93 isdisposed in front of the non-absorber side portion 17 and behind thenon-absorber side portion 17. The free portion 94 extends to both thefront and back sides of the non-absorber side portion 17. Between thedouble gather sheets 95, an elongated elastically stretchable gathermember 96 is disposed at a tip of the free portion or the like. Asillustrated in FIG. 5 , the elastically stretchable gather member 96 isfor raising the free portion 94 by an elastic contraction force in aproduct state.

The three-dimensional gather 90 illustrated in FIGS. 5 and 6 has a formin which the main unit portion 92 is not folded back. However, any knownform can be adopted, such as a form in which a root side portion of themain unit portion 92 rises obliquely toward the center in the widthdirection, and a portion closer to a tip than the intermediate portionrises obliquely outward in the width direction.

As the elastically stretchable gather member 96, a usually used materialsuch as a polystyrene-based rubber, a polyolefin-based rubber, apolyurethane-based rubber, a polyester-based rubber, polyurethane,polyethylene, polystyrene, styrene-butadiene copolymer, silicone, orpolyester can be used. In order to make it difficult to see theelastically stretchable gather member 96 from the outside, theelastically stretchable gather member 96 preferably has a fineness of925 dtex or less, a tension of 150 to 350%, and an interval of 7.0 mm orless. Note that as the elastically stretchable gather member 96, atape-like member having a certain width can be used in addition to athread-like member as in the illustrated embodiment.

Similarly to the top sheet 11, as a material fiber constituting thegather sheet 95, preferably, in addition to a synthetic fiber such as apolyolefin-based fiber including polyethylene and polypropylene, apolyester-based fiber, or a polyamide-based fiber, a regenerated fibersuch as rayon or cupra, and a natural fiber such as cotton can be used.A nonwoven fabric obtained by an appropriate processing method such as aspunbond method, a thermal bond method, a melt blown method, or a needlepunch method can be used. Particularly, a nonwoven fabric having areduced basis weight and excellent air permeability is preferably usedin order to prevent stuffiness. Furthermore, as the gather sheet 95, inorder to prevent urine or the like from passing through the gather sheet95, to prevent rash, and to enhance feeling (dry feeling) to a skin, itis desirable to use a water repellent nonwoven fabric coated with, forexample, a silicone-based, paraffin metal-based, or alkylchromicchloride-based water repellent agent.

(Structure Example of Outer Member)

The outer member 20 extends from a side edge of the inner member 10 inthe side direction. The outer member 20 may have a side edge locatedcloser to the center in the width direction than a side edge of theinner member 10 at a crotch portion as in the illustrated embodiment, ormay be located outward in the width direction. The outer member 20 haslower torso portions T that are front-back direction rangescorresponding to the side seal portions 21, and an intermediate portionL that is a front-back direction range between the lower torso portion Tof the front body F and the lower torso portion T of the back body B.The planar shape of the outer member 20 is formed such that each of bothside edges 29 of the intermediate portion L in the width direction iscurved along a portion around a leg, and has a shape similar to anhourglass as a whole. The outer member 20 may be formed for each of thefront body F and the back body B so as to be separated from each otherin the front-back direction LD at a crotch portion.

The outer member 20 of the example illustrated in FIGS. 1 to 6 has anelastic film stretchable structure 20X in which a stretchable directionED is a width direction WD except for an intermediate portion of theintermediate portion L in the front-back direction. More specifically,as illustrated in FIGS. 2 and 4 to 6 , the elastic film stretchablestructure 20X has the elastic film 30 laminated between the first sheetlayer 20A and the second sheet layer 20B, and as illustrated in FIG. 7 ,the first sheet layer 20A and the second sheet layer 20B are bonded toeach other through through-holes 31 passing through the elastic film 30with many bonded portions 40 arranged at intervals. The first sheetlayer 20A and the second sheet layer 20B may be bonded to each otherindirectly via the elastic film 30 instead of through the through-holes31 of the elastic film 30.

The form illustrated in FIGS. 1 and 2 is a form in which the elasticfilm stretchable structure 20X extends up to a waist portion 23.However, if the elastic film stretchable structure 20X is used for thewaist portion 23, for example, the waist portion 23 is not sufficientlytightened. As illustrated in FIGS. 15 and 16 , the waist portion 23 canhave a stretchable structure by a conventional elongated waist portionelastic member 24 as necessary without having the elastic filmstretchable structure 20X. However, in the illustrated example, at anedge portion of a leg opening in the outer member 20, an elongatedelastically stretchable member extending along the leg opening is notdisposed. The waist portion elastic member 24 is an elongated elasticmember such as a plurality of rubber threads disposed at intervals inthe front-back direction LD, and applies a stretching force so as totighten a lower torso of a body. The waist portion elastic members 24are not disposed substantially in a bundle at close intervals, but threeor more, preferably five or more waist portion elastic members 24 aredisposed at about 3 to 8 mm intervals so as to form a predeterminedstretchable zone. The stretch rate of the waist portion elastic member24 at the time of fixing can be determined appropriately, but can beabout 230 to 320% for a normal adult. As the waist portion elasticmember 24, a rubber thread is used in the illustrated example, but otherelongated stretchable members such as flat rubber may be used. Althoughnot illustrated, a general-purpose form may be adopted in which only theelongated elastically stretchable member such as a rubber thread or flatrubber is disposed without the elastic film stretchable structure 20Xdisposed on the outer member 20.

Although not illustrated, another form may be, for example, a form inwhich the intermediate portion L between the lower torso portion T ofthe front body F and the lower torso portion T of the back body B doesnot have the elastic film stretchable structure 20X, a form in which theelastic film stretchable structure 20X is continuously disposed in thefront-back direction LD from the lower torso portion T of the front bodyF up to the lower torso portion T of the back body B through theintermediate portion L, or a form in which only either the front body For the back body B has the elastic film stretchable structure 20X.Appropriate modifications are also possible.

The shape of each of the bonded portions 40 and the through-holes 31 ina natural length state can be determined appropriately, and can be anyshape such as a perfect circle (see FIGS. 7 and 8 ), an ellipse, apolygon such as a triangle, a rectangle (see FIGS. 9 to 12 ), or arhombus (see FIG. 13(b)), a convex lens shape (see FIG. 13(a)), aconcave lens shape (see FIG. 13(c)), a star shape, or a cloud shape. Thesize of each of the bonded portions 40 is not particularly limited.However, the maximum length thereof is preferably 0.5 to 3.0 mm, andparticularly preferably 0.7 to 1.1 mm. The maximum width 40 x thereof ispreferably 0.1 to 3.0 mm, and is preferably 0.1 to 1.1 mm particularlyin a case of a long shape in an orthogonal direction XD orthogonal tothe stretchable direction ED.

The size of each of the bonded portions 40 only needs to be determinedappropriately. However, if the size is too large, an influence of thehardness of the bonded portion 40 on feeling increases, and if the sizeis too small, a bonded area is small and materials cannot sufficientlybe bonded to each other. Therefore, in a normal case, the area of eachof the bonded portions 40 is preferably about 0.14 to 3.5 mm². The areaof an opening of each of the through-holes 31 only needs to be equal toor larger than the area of the bonded portion 40 because the bondedportion 40 is formed through the through-hole 31. However, the area ofan opening of each of the through-holes 31 is preferably about 1 to 1.5times the area of the bonded portion 40. Note that the area of anopening of the through-hole 31 means a value not in a state of theelastic film 30 alone but in a state of being integrated with the firstsheet layer 20A and the second sheet layer 20B and in a natural lengthstate. When the area of an opening of the through-hole 31 is not uniformin the thickness direction, such as when the area of an opening of thethrough-hole 31 is different between the front and the back of theelastic film 30, the area of an opening of the through-hole 31 means aminimum value.

A planar arrangement of the bonded portions 40 and the through-holes 31can be determined appropriately, but a regularly repeated planararrangement is preferable. In addition to a regularly repeated planararrangement such as an oblique lattice shape as illustrated in FIG.20(a), a hexagonal lattice shape (these are also called a zigzag shape)as illustrated in FIG. 20(b), a square lattice shape as illustrated inFIG. 20(c), a rectangular lattice shape as illustrated in FIG. 20(d), ora parallel lattice (a form in which two groups are disposed such thatmany groups of parallel diagonal rows intersect each other asillustrated in the drawing) shape as illustrated in FIG. 20(e)(including a form in which these are inclined at an angle of less than90 degrees with respect to the stretchable direction ED), a form inwhich a group of the bonded portions 40 (group units may be arrangedregularly or irregularly, and may have a pattern shape or a lettershape) is regularly repeated may be adopted.

When the first sheet layer 20A and the second sheet layer 20B in thebonded portion 40 are bonded to each other through the through-holes 31formed in the elastic film 30, it is desirable that the first sheetlayer 20A and the second sheet layer 20B are not bonded to the elasticfilm 30 except for at least a portion between the first sheet layer 20Aand the second sheet layer 20B in the bonded portion 40.

A means for bonding the first sheet layer 20A and the second sheet layer20B in the bonded portion 40 to each other is not particularly limited.For example, the first sheet layer 20A and the second sheet layer 20B inthe bonded portion 40 may be bonded to each other with a hot meltadhesive or by a bonding means by material welding such as heat sealingor ultrasonic sealing.

When the first sheet layer 20A and the second sheet layer 20B in thebonded portion 40 are bonded to each other through the through-hole 31of the elastic film 30, a form in which the bonded portion 40 is formedby material welding may be any one of a first welding form in which thefirst sheet layer 20A and the second sheet layer 20B are bonded to eachother only with a molten and solidified material 20 m of a most part ora part of at least one of the first sheet layer 20A and the second sheetlayer 20B in the bonded portion 40 (see FIG. 17(a)), a second weldingform in which the first sheet layer 20A and the second sheet layer 20Bare bonded to each other only with a molten and solidified material 30 mof the entire part, a most part, or a part of the elastic film 30 in thebonded portion 40 (see FIG. 17(b)), and a third welding form in whichboth of the first welding form and the second welding form are combined(see FIG. 17(c)), but the second and third welding forms are preferable.Particularly preferably, the first sheet layer 20A and the second sheetlayer 20B are bonded to each other with the molten and solidifiedmaterial 20 m of a part of the first sheet layer 20A and the secondsheet layer 20B and the molten and solidified material 30 m of theentire part or a most part of the elastic film 30 in the bonded portion40. Note that in the third welding form illustrated in FIG. 19(b), themolten and solidified material 30 m of the elastic film 30 representedin white is observed between the molten and solidified materials 20 m ofthe first sheet layer 20A or the second sheet layer 20B represented inblack, whereas in the first welding form illustrated in FIG. 19(a), amolten and solidified material of the elastic film is not observedbetween the molten and solidified materials 20 m of the first sheetlayer 20A or the second sheet layer 20B (white portion represents aboundary of the molten and solidified material 20 m and irregularreflection of the molten and solidified material 20 m).

As in the first adhesion form and the third adhesion form, when thefirst sheet layer 20A and the second sheet layer 20B are bonded to eachother using the molten and solidified material 20 m of a most part or apart of at least one of the first sheet layer 20A and the second sheetlayer 20B as an adhesive, it is preferable not to melt a part of thefirst sheet layer 20A and the second sheet layer 20B because the bondedportion 40 is not hardened. Note that when the first sheet layer 20A andthe second sheet layer 20B are formed of a nonwoven fabric, a form inwhich a part of the first sheet layer 20A and the second sheet layer 20Bdoes not melt includes a form in which cores (including not only a corein a composite fiber but also a center portion of a single componentfiber) of all the fibers of the bonded portion 40 remain unmelted butportions surrounding the cores (including not only a sheath in acomposite fiber but also a portion on a surface layer side of a singlecomponent fiber) melt, and a form in which some fibers do not melt atall, but all the remaining fibers melt or cores thereof remain unmeltedbut portions surrounding the cores melt.

When the first sheet layer 20A and the second sheet layer 20B are bondedto each other using the molten and solidified material 30 m of theelastic film 30 as an adhesive as in the second welding form and thethird welding form, peel strength is high. In the second welding form,manufacture is possible by sandwiching the elastic film 30 between thefirst sheet layer 20A and the second sheet layer 20B under a conditionthat the melting point of at least one of the first sheet layer 20A andthe second sheet layer 20B is higher than the melting point of theelastic film 30 and the heating temperature at the time of forming thebonded portion 40, pressurizing and heating a site to be the bondedportion 40, and melting only the elastic film 30. Meanwhile, in thethird welding form, manufacture is possible by sandwiching the elasticfilm 30 between the first sheet layer 20A and the second sheet layer 20Bunder a condition that the melting point of at least one of the firstsheet layer 20A and the second sheet layer 20B is higher than themelting point of the elastic film 30, pressurizing and heating a site tobe the bonded portion 40, and melting at least one of the first sheetlayer 20A and the second sheet layer 20B and the elastic film 30. Fromsuch a viewpoint, the elastic film 30 preferably has a melting point ofabout 80 to 145° C., the first sheet layer 20A and the second sheetlayer 20B each have a melting point preferably of about 85 to 190° C.,particularly preferably of 150 to 190° C., and a difference between themelting point of each of the first sheet layer 20A and the second sheetlayer 20B and the melting point of the elastic film 30 is preferablyabout 60 to 90° C. The heating temperature is preferably about 100 to150° C.

In the second welding form and the third welding form, when the firstsheet layer 20A and the second sheet layer 20B are formed of a nonwovenfabric, the molten and solidified material 30 m of the elastic film 30may penetrate between fibers over the entire thickness direction of thefirst sheet layer 20A and the second sheet layer 20B in the bondedportion 40 as illustrated in FIG. 18(c). However, a form in which themolten and solidified material 30 m penetrates between fibers up to anintermediate portion in the thickness direction as illustrated in FIGS.17(b), 17(c), and 18(a), or a form in which the molten and solidifiedmaterial 30 m hardly penetrates between fibers of the first sheet layer20A and the second sheet layer 20B as illustrated in FIG. 18(b) achieveshigher flexibility of the bonded portion 40.

FIGS. 21 and 22 illustrate an example of an ultrasonic sealing devicesuitable for forming the second welding form and the third welding form.In this ultrasonic sealing device, for forming the bonded portion 40,the first sheet layer 20A, the elastic film 30, and the second sheetlayer 20B are fed between an anvil roll 60 having protrusions 60 aformed in the pattern of the bonded portions 40 on an outer surfacethereof and an ultrasonic horn 61. At this time, for example, by makinga feeding transfer speed of the elastic film 30 by a feeding drive roll63 and a nip roll 62 on an upstream side slower than the feeding speedafter the anvil roll 60 and the ultrasonic horn 61, the elastic film 30is stretched to a predetermined stretch rate in the MD direction(machine direction, flow direction) in a path from a nip position by thefeeding drive roll 63 and the nip roll 62 to a seal position by theanvil roll 60 and the ultrasonic horn 61. The stretch rate of theelastic film 30 can be set by selecting a speed difference between theanvil roll 60 and the feeding drive roll 63, and can be set to about300% to 500%, for example. Reference numeral 62 represents a nip roll.The first sheet layer 20A, the elastic film 30, and the second sheetlayer 20B fed between the anvil roll 60 and the ultrasonic horn 61 arepressurized between the protrusions 60 a and the ultrasonic horn 61 andheated by ultrasonic vibration energy of the ultrasonic horn 61 whilethe first sheet layer 20A, the elastic film 30, and the second sheetlayer 20B are laminated in this order to melt only the elastic film 30or to melt at least one of the first sheet layer 20A and the secondsheet layer 20B and the elastic film 30. As a result, the through-holes31 are formed in the elastic film 30, and simultaneously the first sheetlayer 20A and the second sheet layer 20B are bonded to each otherthrough the through-holes 31. Therefore, in this case, by selecting thesizes, the shapes, a separation interval, an arrangement pattern in aroll length direction and roll circumferential direction, and the likeof the protrusions 60 a of the anvil roll 60, the area ratio of thebonded portions 40 can be selected.

A reason why the through-holes 31 are formed is not necessarily clear,but is considered to be that portions corresponding to the protrusions60 a of the anvil roll 60 in the elastic film 30 are melted and detachedfrom the surroundings to form holes. At this time, a portion of theelastic film 30 between the adjacent through-holes 31 in the stretchabledirection ED is cut from both sides in the stretchable direction by thethrough-holes 31 as illustrated in FIGS. 7(a), 9(a), and 11(a), andloses a support on both sides in a contraction direction. Therefore, theportion of the elastic film 30 between the adjacent through-holes 31 inthe stretchable direction ED contracts until the center side of theorthogonal direction XD is balanced with the central side of thestretchable direction within a range in which continuity in a directionorthogonal to the contraction direction can be maintained, and thethrough-holes 31 expand in the stretchable direction ED. Then, when thebonded portions 40 are formed in a pattern in which a portion where theelastic film 30 is linearly continuous in the stretchable direction EDremains as in a stretchable region 80 described later, as illustrated inFIGS. 7(d) and 9(d), when contraction occurs to a natural length state,for example, by cutting the elastic film 30 into individual products,the length of the expanded portion of the through-hole 31 in thestretchable direction ED contracts until a gap is not formed between thethrough-hole 31 and the bonded portion 40. Meanwhile, when the bondedportions 40 are formed in a pattern in which a portion where the elasticfilm 30 is linearly continuous in the stretchable direction ED is notpresent as in a non-stretchable region 70 described later, asillustrated in FIG. 11(d), when contraction occurs to a natural lengthstate, for example, by cutting the elastic film 30 into individualproducts, the length of the expanded portion of the through-hole 31 inthe stretchable direction ED hardly contracts. Therefore, a large gapremains between the through-hole 31 and the bonded portion 40.

A material constituting the first sheet layer 20A and the second sheetlayer 20B can be used without particular limitation as long as having asheet shape. However, a nonwoven fabric is preferably used fromviewpoints of air permeability and flexibility. The nonwoven fabric isnot particularly limited concerning a raw material fiber thereof.Examples thereof include a synthetic fiber such as a polyolefin-basedfiber including polyethylene and polypropylene, a polyester-based fiber,or a polyamide-based fiber, a regenerated fiber such as rayon or cupra,a natural fiber such as cotton, and a mixed fiber and a composite fiberin which two or more kinds of these fibers are used. Furthermore, thenonwoven fabric may be manufactured by any processing. Examples of aprocessing method include a known method such as a spunlace method, aspunbond method, a thermal bond method, a melt blown method, a needlepunch method, an air through method, and a point bond method. In a casewhere a nonwoven fabric is used, the nonwoven fabric preferably has abasis weight of about 12 to 20 g/m². Furthermore, a part or the entirepart of the first sheet layer 20A and the second sheet layer 20B may bea pair of facing layers obtained by folding back a single material. Forexample, as in the illustrated embodiment, in the waist portion 23, byusing a constituent material located outside as the second sheet layer20B, and using a folded-back portion 20C obtained by folding back awaist opening edge thereof to an internal surface side as the firstsheet layer 20A, the elastic film 30 can be interposed therebetween.Moreover, in a portion other than the waist portion 23, by using aconstituent material located inside as the first sheet layer 20A, andusing a constituent material located outside as the second sheet layer20B, the elastic film 30 can be interposed therebetween. Of course, bydisposing the constituent material of the first sheet layer 20A and theconstituent material of the second sheet layer 20B individually over theentire front-back direction LD without folding back the constituentmaterials, the elastic film 30 can also be interposed between theconstituent material of the first sheet layer 20A and the constituentmaterial of the second sheet layer 20B.

The elastic film 30 is not particularly limited, and can be a non-porousfilm or a film having many holes and slits for air permeation as long asbeing a thermoplastic resin film having elasticity in itself.Particularly, the elastic film 30 preferably has a tensile strength of 8to 25 N/35 mm in the width direction WD (stretchable direction ED, MDdirection), a tensile strength of 5 to 20 N/35 mm in the front-backdirection LD (orthogonal direction XD, CD direction), a tensileelongation of 450 to 1050% in the width direction WD, and a tensileelongation of 450 to 1400% in the front-back direction LD. The thicknessof the elastic film 30 is not particularly limited, but is preferablyabout 20 to 40 μm.

(Stretchable Region)

A region having the elastic film stretchable structure 20X in the outermember 20 can stretch and contract in the width direction WD. In otherwords, the region has a stretchable region that contracts in the widthdirection WD by a contraction force of the elastic film 30 in a naturallength state and is extensible in the width direction WD at the time ofwearing. Such a stretchable region can be formed by bonding the firstsheet layer 20A and the second sheet layer 20B to each other through thethrough-holes 31 of the elastic film 30 at many places with intervals ina state where the elastic film 30 is stretched in the width directionWD. In order to exhibit sufficient elasticity, the through-holes 31 andthe bonded portions are preferably disposed at intervals in the widthdirection WD and the front-back direction LD (orthogonal direction XD)orthogonal thereto so as to have a portion 32 where the elastic film 30is linearly continuous in the width direction WD.

In a natural length state, as illustrated in FIGS. 7(d) and 9(d), thestretchable region 80 swells in a direction in which the first sheetlayer 20A and the second sheet layer 20B between the bonded portions 40are separated from each other, and contraction wrinkles 25 extending inthe front-back direction LD are formed. As illustrated in FIGS. 7(c) and9(c), the contraction wrinkles 25 are stretched but remain even in awearing state in which the stretchable region 80 stretches to someextent in the width direction WD. As in the illustrated embodiment, whenthe first sheet layer 20A and the second sheet layer 20B are not bondedto the elastic film 30 except for at least a portion between the firstsheet layer 20A and the second sheet layer 20B in the bonded portion 40,as can be seen from FIGS. 7(c) and 9(c) assuming a wearing state andFIGS. 7(a), 7(b), 9(a), and 9(b) assuming unfolded states of the firstsheet layer 20A and the second sheet layer 20B, in these states, a gapis formed between the through-hole 31 in the elastic film 30 and thebonded portion 40, and air permeability is imparted by this gap even ifa material of the elastic film 30 is a non-porous film or sheet. In anatural length state illustrated in FIGS. 7(d) and 9(d), thethrough-hole 31 is narrowed by contraction of the elastic film 30, and agap is hardly formed between the through-hole 31 and the bonded portion40. Note that the state of the contraction wrinkles 25 in a wearingstate and in a natural length state also appears in FIGS. 8 and 10 .

It is desirable that the elongation at elastic limit of the stretchableregion 80 in the width direction WD is 200% or more (preferably 265 to295%). The elongation at elastic limit of the stretchable region 80 issubstantially determined by the stretch rate of the elastic film 30 atthe time of manufacture, but decreases due to factors that inhibitcontraction in the width direction WD on the basis of the stretch rate.A main one of such inhibition factors is the ratio of the length 40 x ofthe bonded portion 40 with respect to unit length in the width directionWD. The larger this ratio is, the lower the elongation at elastic limitis. In a normal case, the length 40 x of the bonded portion 40 has acorrelation with the area ratio of the bonded portions 40. Therefore,the elongation at elastic limit of the stretchable region 80 can beadjusted by the area ratio of the bonded portions 40.

A stretch stress of the stretchable region 80 can be adjusted mainly bythe sum of the widths 32 w of the portions 32 where the elastic film 30is linearly continuous in the width direction WD. The width 32 w of theportion 32 where the elastic film 30 is linearly continuous in the widthdirection WD is equal to an interval 31 d between the through-holes 31in contact with both side edges of the continuous portion 32 in thefront-back direction LD. The interval 31 d between the through-holes 31is equal to an interval 40 d between the bonded portions 40 in contactwith both side edges of the continuous portion in the front-backdirection LD when the length 31 y of the through-hole 31 in thefront-back direction LD is equal to the length 40 y of the bondedportion 40 in the front-back direction LD (for example, when theabove-described method for simultaneously forming the through-holes 31and the bonded portions 40 is adopted). Therefore, in this case, thestretch stress of the stretchable region 80 can be adjusted by the ratioof the length 40 y of the bonded portion 40 with respect to unit lengthin the front-back direction LD. In a normal case, the length 40 y of thebonded portion 40 has a correlation with the area ratio of the bondedportions 40. Therefore, the stretch stress of the stretchable region 80can be adjusted by the area ratio of the bonded portions 40. A stretchstress at the time of stretch to 50% of the elastic limit can be takenas a standard of the stretch stress of the stretchable region 80.

The area ratio of the bonded portions 40 and the area of each of thebonded portions 40 in the stretchable region 80 can be determinedappropriately, but are preferably within the following ranges in anormal case.

Area of bonded portion 40: 0.14 to 3.5 mm² (particularly 0.14 to 1.0mm²)

Area ratio of bonded portions 40: 1.8 to 19.1% (particularly 1.8 to10.6%)

As described above, the elongation at elastic limit and the stretchstress of the stretchable region 80 can be adjusted by the area of thebonded portion 40. Therefore, not by making the pattern of the bondedportions 40 in the stretchable region 80 uniform as illustrated in FIG.2 , but by disposing a plurality of regions having different area ratiosof the bonded portions 40 in the stretchable region 80 as illustrated inFIG. 15 , fitting can be changed according to a site. In the formillustrated in FIG. 15 , a region 81 extending obliquely along a root ofa leg in the front body F and an edge region 82 of a leg opening eachhave a higher area ratio of the bonded portions 40 than the otherregions, and therefore has a weak stretch stress and stretches andcontracts flexibly. An ilium facing region 83 in the back body B and theedge region 82 of the leg opening also each have a higher area ratio ofthe bonded portions 40 than the other regions, and therefore have a weakstretch stress and stretches and contracts flexibly. In the illustratedexample, a region 84 that is an intermediate portion of a portionoverlapping with the inner member 10 in the front body F in the widthdirection WD has a still higher area ratio of the sheet bonded portions40 than the other regions, and has a still weaker stretch stress andstill smaller elongation at elastic limit.

(Non-Stretchable Region)

In the example illustrated in FIG. 2 , the entire stretchable structure20X of the elastic film 30 is set to the stretchable region 80, and anon-stretchable region is not included. However, in a region having theelastic film stretchable structure 20X, as illustrated in FIG. 15 , anon-stretchable region 70 can be disposed, for example, on at least oneside of the stretchable region 80 in the width direction. Arrangement ofthe stretchable region 80 and the non-stretchable region 70 can bedetermined appropriately. In a case of the outer member 20 of theunderpants-type disposable diaper as in the present embodiment, aportion overlapping with the absorber 13 is a region that does not needto stretch or contract. Therefore, as in the illustrated embodiment, apart or the entire part of a portion overlapping with the absorber 13(desirably including almost an entire inner and outer fixed region 10B)is preferably set to the non-stretchable region 70. Of course, thenon-stretchable region 70 can be disposed from a region overlapping withthe absorber 13 to a region not overlapping with the absorber 13 locatedin the width direction WD or the front-back direction LD, or can bedisposed only in the region not overlapping with the absorber 13.

The non-stretchable region 70 is a region in which the elastic film 30is continuous in the width direction WD but which does not have alinearly continuous portion in the width direction WD due to thepresence of the through-hole 31. Therefore, in a state where the elasticfilm 30 stretches in the width direction WD, even if the entire elasticfilm stretchable structure 20X including both the stretchable region 80and the non-stretchable region 70 is formed by bonding the first sheetlayer 20A and the second sheet layer 20B to each other through thethrough-holes 31 of the elastic film 30 at intervals in the widthdirection WD and the front-back direction LD orthogonal thereto to formthe many bonded portions 40, as illustrated in FIG. 11 , in thenon-stretchable region 70, the elastic film 30 is not linearlycontinuous in the width direction WD. Therefore, a contraction force ofthe elastic film 30 hardly acts on the first sheet layer 20A and thesecond sheet layer 20B, elasticity almost disappears, and an elongationat elastic limit is close to 100%. In such a non-stretchable region 70,the first sheet layer 20A and the second sheet layer 20B are bonded toeach other with many bonded portions 40 arranged at intervals, and thebonded portions 40 are not continuous. Therefore, reduction inflexibility is prevented. In other words, the stretchable region 80 andthe non-stretchable region 70 can be formed by presence or absence of aportion where the elastic film 30 is not linearly continuous in thewidth direction WD. In addition, continuity of the elastic film 30remains even in the non-stretchable region 70. As can be seen from FIG.12 , an independent cut piece of the elastic film 30 does not remain,and wrinkles are not formed. Therefore, appearance is very good, and airpermeability in the thickness direction due to the through-holes 31 isensured. The non-stretchable region 70 preferably has an elongation atelastic limit of 120% or less (preferably 110% or less, more preferably100%) in the width direction WD.

An arrangement pattern of the through-holes 31 in the elastic film 30 inthe non-stretchable region 70 can be determined appropriately. However,when a zigzag arrangement is formed as illustrated in FIG. 11 , and apattern in which a central interval 31 e between the through-holes 31 inthe front-back direction LD is shorter than the length 31 y of thethrough-hole 31 in the front-back direction LD is formed, linearcontinuity in the width direction WD can be almost completely eliminatedwhile continuity of the elastic film 30 is maintained, and appearance isalso preferable as illustrated in FIG. 12 . In this case, a centralinterval 31 f between the through-holes 31 in the width direction WD ismore preferably shorter than a length 31 x of the through-hole 31 in thewidth direction WD.

In a normal case, particularly in a case where the elastic film 30 has astretch stress of 4 to 12 N/35 mm when the elastic film 30 is stretchedfour times in the width direction WD, in a state where thenon-stretchable region 70 is stretched to an elastic limit in the widthdirection WD, the central interval 31 e between the through-holes 31 inthe front-back direction LD is preferably 0.4 to 2.7 mm, and the length31 y of the through-hole 31 in the front-back direction LD is preferably0.5 to 3.0 mm, and particularly preferably 0.7 to 1.1 mm. The centralinterval 31 f between the through-holes 31 in the width direction WD ispreferably 0.5 to 2 times, and particularly preferably 1 to 1.2 timesthe length 31 y of the through-hole 31 in the front-back direction LD.The length 31 x of the through-hole 31 in the width direction WD ispreferably 1.1 to 1.8 times, and particularly preferably 1.1 to 1.4times the central interval 31 f between the through-holes 31 in thewidth direction WD. Note that in a state where the non-stretchableregion 70 is stretched to an elastic limit in the width direction WD (inother words, in a state where the first sheet layer 20A and the secondsheet layer 20B are completely unfolded), the central interval 31 fbetween the through-holes 31 in the width direction WD is equal to acentral interval 40 f between the bonded portions 40 in the widthdirection WD, the central interval 31 e between the through-holes 31 inthe front-back direction LD is equal to a central interval 40 e betweenthe bonded portions 40 in the front-back direction LD, and the length 31y of the through-hole 31 in the front-back direction LD is equal to thelength 40 y of the bonded portion 40 in the front-back direction LD.

In the non-stretchable region 70, when the first sheet layer 20A and thesecond sheet layer 20B are not bonded to the elastic film 30 except fora portion between the first sheet layer 20A and the second sheet layer20B in the bonded portion 40, and a gap is formed by separating aperipheral edge of the through-hole 31 of the elastic film 30 from thebonded portion 40 on both sides of the bonded portion 40 in the widthdirection in a natural length state, this gap imparts air permeabilityall the time even if a material of the elastic film 30 is a non-porousfilm or sheet. Therefore, this is preferable. When the above-describedmethod for simultaneously forming the through-holes 31 and the bondedportions 40 is adopted, this state naturally occurs regardless of theshapes of the bonded portions 40 and the like.

The shape of each of the bonded portions 40 and the through-holes 31 ina natural length state is not particularly limited. However, each of thebonded portions 40 and the through-holes 31 in a natural length statedesirably has a small area from a viewpoint of flexibility. In order toeliminate linear continuity of the elastic film 30 in the widthdirection WD, a shape that is long in the front-back direction LD isdesirable. Therefore, an ellipse, a rectangle (see FIGS. 11 and 13 (d)),a rhombus (see FIG. 13(b)), a convex lens shape (see FIG. 13(b)), and aconcave lens shape (see FIG. 13(c)) which are long in the front-backdirection LD are preferable. However, if the shape has a corner with anacute angle like a rhombus, the elastic film 30 is easily broken.Meanwhile, a convex lens shape is preferable because welding of thebonded portion 40 is stable, and a concave lens shape is preferablebecause the area can be further reduced.

The area ratio of the bonded portions 40 and the area of each of thebonded portions 40 in the non-stretchable region can determined beappropriately, but are preferably within the following range in a normalcase because the non-stretchable region 70 does not become hard due to asmall area of each of the bonded portions 40 and a low area ratio of thebonded portions 40.

Area of bonded portion 40: 0.10 to 0.75 mm² (particularly 0.10 to 0.35mm²)

Area ratio of bonded portions 40: 4 to 13% (particularly 5 to 10%)

As described above, the elongation at elastic limit of thenon-stretchable region 70 can be changed according to the arrangementpattern of the through-holes 31, the size of each of the through-holes31, and the central interval therebetween. Therefore, although notillustrated, the arrangement pattern of the through-holes 31, the sizeof each of the through-holes 31, and the central interval therebetweencan be made different among a plurality of places in the stretchableregion 80 or among the plurality of non-stretchable regions 70. Forexample, it is one preferable form to make the elongation at elasticlimit in the non-stretchable region 70 of the front body F larger thanthe elongation at elastic limit in the non-stretchable region 70 of theback body B.

The non-stretchable region 70 can also adopt another form that cancelselasticity, such as a form in which the non-stretchable region 70 has alinearly continuous portion in the width direction WD like thestretchable region, but the elongation at elastic limit is significantlylow because the area ratio of the bonded portions 40 is higher than thatin the stretchable region, and the elongation at elastic limit isspecifically 130% or less, or a form in which the elastic film 30 is cutat one place or a plurality of places in the width direction WD like aconventional stretchable structure using a rubber thread.

(Overlapping Portion of Elastic Film)

Characteristically, the stretchable region 80 includes the plurality ofelastic films 30 disposed so as to have an overlapping portion 33. Thenumber of laminated layers of the elastic films 30 in a first region 26located in an intermediate portion of the stretchable region 80 in thefront-back direction LD (orthogonal direction XD) is different from thatin each of second regions 27 adjacent to both sides of the first region26. As a result, the number of laminated layers of the elastic films 30is different between the first region 26 and the second region 27.Therefore, a contraction force at the time of stretch can be madedifferent regardless of a change in the pattern of the bonded portion 40or the stretch rate of the elastic film 30. That is, if the first region26 and the second region 27 have the same pattern of the bonded portions40 and the same stretch rate of the elastic film 30, a contraction forcein a region with a large number of laminated layers is relativelystronger, and a contraction force in a region with a small number oflaminated layers is relatively weaker.

In manufacture, for example, as illustrated in FIGS. 21 and 22 , theplurality of elastic films 30 is fed between the anvil roll 60 and theultrasonic horn 61 so as to have the overlapping portion 33, and thefirst sheet layer 20A and the second sheet layer 20B can be bonded toeach other.

Either the first region 26 or the second region 27 may have a largernumber of laminated layers of the elastic films 30. As in the examplesillustrated in FIGS. 1, 2, and 4 , and the examples illustrated in FIGS.15 and 16 , a structure is preferable in which one stretchable region 80includes the elastic film 30 extending from one of the second regions 27to the first region 26, and the elastic film 30 extending from the othersecond region 27 to the first region 26, each of the second regions 27includes only one elastic film 30, and the first region 26 includes twoelastic films 30 overlapping with each other. In this case, a simplestructure in which the number of elastic films 30 per stretchable region80 is the minimum two, and the number of laminated layers of the elasticfilms 30 is also minimum is obtained. Therefore, a risk of makingmanufacture difficult, such as difficulty in forming the bonded portions40, is reduced. As in the example illustrated in FIG. 23 , when three ormore elastic films 30 are used per stretchable region 80, a contractionforce can be changed so as to be suitable for more sites. In the exampleillustrated in FIG. 23 , the elastic film 30 over the entire stretchableregion 80 is basically used, and the elastic film 30 is added to a sitewhere a strong contraction force should be exerted, that is, to oneintermediate portion in the front-back direction LD and an end portionin the front-back direction LD (the waist portion 23 in the illustratedexample, but the elastic film 30 may be disposed at an end portion of aleg opening side instead of the waist portion 23 or together with thewaist portion 23). However, the elastic film 30 can be added to aplurality of places in an intermediate portion in the front-backdirection LD.

When the plurality of elastic films 30 is used and the number oflaminated layers of the elastic films 30 is changed depending on a siteas described above, unlike a conventional form in which the number oflaminated layers is increased by folding, the number of portions with alarge number of laminated layers and arrangement thereof are notlimited, and various changes are possible. For example, as in theexample illustrated in FIGS. 1, 2 and 4 , and the example illustrated inFIGS. 15 and 16 , when the outer member 20 of the front body F has thestretchable region 80 at least in the lower torso portion T, the outermember 20 of the back body B has the stretchable region 80 extendingfrom the lower torso portion T to the intermediate portion L, and acontraction force of each of the stretchable regions 80 is changed inthe front-back direction LD by the two elastic films 30 consisting ofthe elastic film 30 located on the waist opening side and the elasticfilm 30 located on the opposite side (center side of the diaper in thefront-back direction), as illustrated in FIG. 14 , preferably, thestretchable region 80 of the outer member 20 of the front body F has thefirst region 26 in the lower torso portion T and has the second region27 in the other regions, and the stretchable region 80 of the outermember 20 of the back body B has the first region 26 in the intermediateportion L and has the second region 27 in the other regions. Bydisposing the first region 26 in which the two elastic films 30 overlapwith each other and the second region 27 including only one elastic film30 asymmetrically in a front-back direction as described above,favorable fitting to a lower abdomen portion and a lower gluteal region(gluteal groove) where a gap is easily generated is achieved. Inaddition, since the position of the first region 26 of the front body Fis different from the first region 26 of the back body B in the sideseal portion 21, the number of laminated layers of a material in theside seal portion 21 does not become locally too large. Therefore,deterioration of wearing feeling and sealing failure of the side sealportion 21 are prevented.

As the plurality of elastic films 30 disposed in one stretchable region80, elastic films having the same stretch stress may be used. However,when elastic films having different stretch stresses are used, acontraction force can be changed at three or more stages together with achange in the number of laminated layers. For example, as the elasticfilms 30 in the examples illustrated in FIGS. 1, 2, and 4 , and in theexamples illustrated in FIGS. 15 and 16 , when elastic films 30 havingdifferent stretch stresses at the time of 4-times stretch in the widthdirection WD are used, a contraction force can be made different amongthe three regions consisting of one of the second regions 27, the firstregion 26, and the other second region 27 while a simple structure ismaintained. Particularly, if the elastic film 30 located on the waistopening side has a weaker stretch stress at the time of 4-times stretchin the stretchable direction ED than the elastic film 30 located on theopposite side (center side of the diaper in the front-back direction), aportion where a gap is easily generated can be firmly tightened at thetime of wearing, and a contraction force of a portion closer to a waistopening than the portion where a gap is easily generated can beminimized to reduce tightening feeling on the waist opening side.Therefore, this is preferable.

A case where an elongation at elastic limit of the one of the secondregions 27 is different from that of the other second region 27, and thelarger elongation at elastic limit is the same as the elongation atelastic limit of the first region 26 is also preferable. Such astructure having different elongation at elastic limits can be formed bymaking the stretch rates of the respective elastic films 30 differentwhen the first sheet layer 20A and the second sheet layer 20B are bondedto each other in manufacture. For example, as in a sheet bonding deviceillustrated in FIGS. 21 and 22 , if the feeding drive roll 63 and thenip roll 62 are disposed independently with respect to each of theelastic films 30, and feeding transfer speeds of the elastic films 30feeding to the anvil roll 60 and the ultrasonic horn 61 are madedifferent from one another, the elongation at elastic limit of one ofthe second regions 27 is different from that of the other second region27, and the larger elongation at elastic limit is the same as theelongation at elastic limit of the first region 26.

In this structure with different elongation at elastic limits, when thestretchable region 80 is stretched in the width direction WD from aninitial stage at which both the elastic films 30 are in a natural lengthstate, the stretchable region 80 comes to a wearing stage at which boththe elastic films 30 are in a stretched state through an intermediatestage at which one of the elastic films 30 is in a natural length state,and the other elastic film 30 is in a stretched state. Therefore, whenthe stretchable region 80 is stretched for wearing, the first region 26initially stretches with the same stretch stress as the second region 27with a larger elongation at elastic limit, and the stretch stress is thestrongest at a wearing stage. Therefore, the diaper is easily worn, andobtains firm fitting in a wearing state.

In the structure with different elongation at elastic limits, theelastic films 30 having different stretch stresses can be used, but theelastic films 30 having the same stretch stress can also be used. Thelatter is more advantageous than the former from a viewpoint of materialcost.

(Others)

The above-described stretchable structure 20X is applicable not only toan underpants-type disposable diaper but also to other stretchableportions such as a lower torso or a fastening tape of a tape-typedisposable diaper, a three-dimensional gather widely used for a generalabsorbent article, and a planar gather. In the illustrated example, thestretchable direction is set to the width direction, but can also be setto both the width direction and the front-back direction.

<Explanation of Terms in Specification>

The following terms in the specification have the following meaningsunless otherwise specified in the specification.

-   -   “Front body” and “back body” mean a front portion and a back        portion with the center of an underpants-type disposable diaper        in the front-back direction as a boundary, respectively. A        crotch portion means a front-back direction range including the        center of an underpants-type disposable diaper in the front-back        direction. When an absorber has a narrowing portion, the crotch        portion means a front-back direction range of the portion having        the narrowing portion.    -   “Elastic limit elongation” means stretch at an elastic limit in        the stretchable direction ED (in other words, a state where the        first sheet layer and the second sheet layer are completely        unfolded), and represents the length at the elastic limit in        terms of a percentage when a natural length is 100%.    -   “Area ratio” means the ratio of a target portion with respect to        a unit area, and represents a ratio obtained by dividing the        total area of a target portion (for example, bonded portions 40        and through-holes 31) in a target region (for example,        stretchable region 80, non-stretchable region 70, main        stretchable portion, and buffer stretchable portion) by the area        of the target region in terms of a percentage. Particularly,        “area ratio” in a region having a stretchable structure means an        area ratio in a state where an article is stretched to an        elastic limit in the stretchable direction ED. In a form in        which many target portions are disposed at intervals, it is        desirable to set a target region to a size including 10 or more        target portions and to determine the area ratio.    -   “Stretch rate” means a value obtained when a natural length is        100%.    -   “Basis weight” is measured as follows. A sample or a test piece        is predried and then left in a test chamber or an apparatus in a        standard state (test location is at a temperature of 23±1° C.        and a relative humidity of 50±2%) so as to have a constant        weight. Predrying refers to causing a sample or a test piece to        have a constant weight in an environment of a temperature of        100° C. Note that fibers having an official moisture regain of        0.0% do not have to be predried. A sample of 100 mm×100 mm in        size is cut out from a test piece having a constant weight using        a template for sampling (100 mm×100 mm). The weight of the        sample is measured. The weight is multiplied by 100 to calculate        the weight per square meter to be used as a basis weight.    -   The thickness of an absorber is measured by using a thickness        meter (Peacock, dial thickness gauge large type, model J-B        (measurement range: 0 to 35 mm) or model K-4 (measurement range:        0 to 50 mm)) manufactured by Ozaki Mfg. Co., Ltd. and making the        sample and the thickness meter horizontal.    -   “Thickness” other than the above is automatically measured under        conditions that a load is 0.098 N/cm² and a pressing area is 2        cm² using an automatic thickness meter (KES-G5 handy compression        measuring program).    -   “Tensile strength” and “tensile elongation (breaking        elongation)” mean values measured by setting an initial chuck        interval (distance between marked lines) to 50 mm and setting a        tensile speed to 300 mm/min according to JIS K7127: 1999        “Plastics-Test method for tensile properties-” except that a        test piece has a rectangular shape with a width of 35 mm and a        length of 80 mm.    -   “Stretch stress” means a tensile stress (N/35 mm) measured at        the time of stretch in an elastic region by a tensile test in        which an initial chuck interval (distance between marked lines)        is set to 50 mm and a tensile speed is set to 300 ram/min        according to JIS K7127: 1999 “Plastics-Test method for tensile        properties-”. The degree of stretch can be determined        appropriately depending on a test target. A test piece        preferably has a rectangular shape with a width of 35 mm and a        length of 80 mm or more. However, if a test piece with a width        of 35 mm cannot be cut out, a test piece with a width that can        be cut out is prepared, and a value obtained by converting a        measured value into a value with a width of 35 mm is used. Even        when a target region is small as in an elastic film built into a        product or a sufficiently large test piece cannot be collected,        if the magnitude of a stretch stress is compared, at least        comparison is possible appropriately even with small test pieces        as long as the test pieces have the same size.    -   “Unfolded state” means a flatly unfolded state without        contraction or slackness.    -   The size of each portion means a size not in a natural length        state but in an unfolded state unless otherwise specified.    -   In a case where environmental conditions in a test and a        measurement are not described, the test and the measurement are        performed in a test room or an apparatus in a standard state        (test location is at a temperature of 23±1° C. and a relative        humidity of 50±2%).

INDUSTRIAL APPLICABILITY

The present invention can be used for a general disposable wearablearticle with a stretchable region, for example, various disposablediapers such as tape-type and pad-type disposable diapers or a sanitarynapkin, in addition to an underpants-type disposable diaper as in theabove example.

REFERENCE SIGNS LIST

-   -   10 Inner member    -   10B Inner and outer fixed region    -   11 Top sheet    -   12 Liquid impervious sheet    -   13 Absorber    -   13N Narrowing portion    -   14 Wrapping sheet    -   17 Non-absorber side portion    -   20 Outer member    -   20A First sheet layer    -   20B Second sheet layer    -   20C Folded-back portion    -   20X Elastic film stretchable structure    -   21 Side seal portion    -   23 Waist portion    -   24 Waist portion elastic member    -   25 Contraction wrinkles    -   30 Elastic film    -   31 through-hole    -   40 Bonded portion    -   70 Non-stretchable region    -   80 Stretchable region    -   90 Three-dimensional gather    -   93 Fallen portion    -   94 Free portion    -   95 Gather sheet    -   96 Elastically stretchable gather member    -   B Back body    -   ED Stretchable direction    -   F Front body    -   L Intermediate portion    -   LD Front-back direction    -   T Lower torso portion    -   WD Width direction    -   XD Orthogonal direction    -   33 Overlapping portion    -   26 First region    -   27 Second region

The invention claimed is:
 1. A disposable wearable article comprising anelastic film stretchable structure in which a plurality of elastic filmsis laminated between a first sheet layer and a second sheet layer, andthe first sheet layer and the second sheet layer are bonded to eachother through holes passing through the plurality of elastic films orvia the plurality of elastic films with many bonded portions arranged atintervals, wherein the elastic film stretchable structure includes astretchable region that elastically stretches and contracts together,the disposable wearable article is an underpants-type disposablewearable article, wherein both sides of an outer member in a front bodyare bonded to both sides of the outer member in a back body to form aside seal portion and to form a waist opening and a pair of left andright leg openings, the outer member includes a front body lower torsoportion, a back body lower torso portion, and an intermediate portionlocated therebetween, an inner member is attached to the outer memberand extends from the front body to the back body via a crotch portion,each of the outer member in the front body and the outer member of theback body has the stretchable region, each of the stretchable region ofthe front body and the stretchable region of the back body includes theplurality of elastic films disposed so as to have an overlappingportion, each of the stretchable region of the front body and thestretchable region of the back body has a different number of laminatedlayers of the plurality of elastic films between a first regionextending in a stretchable direction located in an intermediate portionof the stretchable region in a direction orthogonal to the stretchabledirection and in each of second regions adjacent to both sides of thefirst region, the plurality of elastic films comprises a first elasticfilm extending from one of the second regions to the first region, and asecond elastic film extending from the other second region to the firstregion, wherein the one of the second regions includes only the firstelastic film, the other second region includes only the second elasticfilm, and the first region includes the first elastic film and thesecond elastic film, each of the first elastic film and the secondelastic film extends from one of the side seal portions to the otherside seal portion, and a location of the first region of the front bodyin the side seal portion and a location of the first region of the backbody in the side seal portion are different.
 2. The disposable wearablearticle according to claim 1, wherein an elongation at elastic limit ofthe one of the second regions is different from that of the other secondregion, and the larger elongation at elastic limit thereof is the sameas the elongation at elastic limit of the first region.
 3. Thedisposable wearable article according to claim 1, wherein the outermember of the front body has the first region in the lower torsoportion, and the outer member of the back body has the first region inthe intermediate portion.
 4. The disposable wearable article accordingto claim 3, wherein in the first elastic film and the second elasticfilm, a stretch stress at the time of 4-times stretch in the stretchabledirection in the elastic film on a waist opening side is less than thatin the elastic film on the opposite side.